11 Irregular Plural Words That Sound Completely Wrong—But Aren’t

We all know irregular plurals like “geese” and “mice.” But have you ever heard of “beeves” or “sphinges”? Laugh yourself stupid with our smart grammar quiz.

The plural of “beef” is…

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The plural of beef is… beeves! This is true only for “beef” in the sense of “cow”; If you’re talking about arguments between whiny celebrities on Twitter, then those are beefs. You’ve probably been saying these 24 things wrong the whole time.

The plural of “opus” is…

The plural of “sphinx” is…

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The plural of sphinx is… sphinges! (Though “sphinxes” is an acceptable secondary option.)

The plural of “biceps” is…

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The plural of biceps is… bicepses! That’s right: “biceps” is a singular word, literally translated from the Latin for “two-headed” (each of your biceps connects to the upper arm via two heads, one short and one long.) These 7 punctuation mistakes are making you look stupid.

The plural of “cul-de-sac” is…

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The plural of cul-de-sac is… culs-de-sac. In French, cul-de-sac literally translates to “bottom of a sack.” So, weirdly, the plural culs-de-sac becomes “Bottoms of a sack.” (That sack’s got back!)

The plural of “octopus” is…

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The plural of octopus is… octopuses! No—NOT octopi. Here’s the deal: “Octopi” is how you would make the word plural in Latin; unfortunately, “octopus” is not a Latin word—it’s Greek. The Greek way to make octopus plural is “Octopodes.” So, why don’t we say that? Because, linguists say, when you add a word to the English lexicon, you give all forms of the word an English inflection. So, octopus becomes octopuses. Silly as it sounds, stick with that.

The plural of “Prius” is…

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The plural of Prius is… Prii! Toyota officially announced this new word after a 2011 vote of more than 1.8 million people. Prii trounced runners-up (another weird plural) including Priuses, Prium, and Prien.